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Topic: Alkalinity reduction using lime (Read 2454 times)

I have been busy over the last few weeks writing another article for braukaiser.com. This time about reducing water alkalinity by using slacked lime, which is a commonly used procedure in large scale brewing but rarely used by home brewers. Though I doubt that I’ll convince many of you to give it a try since it doesn’t work for types of high alkalinity water and it takes more preparation that dilution, building from RO water or addition of salts it is a very elegant way of treating brewing water.

This article grew rather large. As I was writing it I found a lot of information about the subject that I just had to mention as well.

Thanks for the work on that Kai. I have been looking into possibly using slaked lime to reduce the alkalinity in the water for my upcoming project. I will most certainly give it a thorough read. Hope you are up to answering a lot of questions.

Wow! I hope this piece is going to end up in Zymurgy? I've experimented once before (after being so inspired by a mega-brewery visit) using lime, although it's definitely more work to get the same results.

Wow! I hope this piece is going to end up in Zymurgy? I've experimented once before (after being so inspired by a mega-brewery visit) using lime, although it's definitely more work to get the same results.

I can pitch it to Jill as a possible Zymurgy article but, to be honest, how many Zymurgy readers would really be interested in this rather technical feature. I might give it a try as a piece for the Geeks column but that puts a tight constraint on the amount of words I can use.

Very, very nice work Kai. You are brilliant. I don't really have a need for this technique, but it is interesting and a great "go to" recourse for those in need of reducing their alkalinity. As I have said before, I will say it again...you are the "King of all Imperial Beer Geeks".

The lime addition will make your water softer as well leaving the precipitate behind where ever it may end up (in the mash tun/kettle/carboy)?

I think you have to change the wording a bit: Lime addition can make the water softer with lower alkalinity by precipitating calcium carbonate from it. But you have to make sure you remove that precipitate before you use the water for brewing. Otherwise it will dissolve again during the brewing process.

I'm having a hard time understanding this and I can't run the spread sheet on my Mac. If my water contains 45 ppms of calcium and has an alkalinity of 129 as CaCo3 it appears I will have to add gypsum or calcium carbonate to actually lower my alkalinity. Correct? Because the calcium hardness of the water is only 112.5 ppm as CaCo3.

So I am not sure how much calcium I have to add to reduce my alkalinity by how much with a slaked lime addition(?). I won't lie, the chemistry is daunting to me. I was an art major....

I'm having a hard time understanding this and I can't run the spread sheet on my Mac.

stupid Mac

But let me try to explain this:

you have alkalinity worth ~130 ppm CaCO3. This also means that your bicarbonate content is worth 130 ppm CaCO3. Now you only have Calcium that is only worth 110 ppm as CaCO3. Since the lime treatment bascially causes the calcium and the bicarbonate to form chalk (CaCO3) your water only has the ingredients for 110 ppm CaCO3. Your calcium is the limiting ingredient here. The nice thing about lime is that you don't have to consider its amount in these calculations since all the added lime will also precipitate as chalk. It's almost acting like a catalyst.

Now that we know that we need to add more calcium we can try calculating it. Let's say we want to precipitate all alkalinity worth 130ppm CaCO3. This means we need at least the same amont of calcium. But we also need some calcium left over such that the brewing water can have at least 50 ppm (actual 50 mg/l) calcium. Those 50 ppm are worth ~120 ppm CaCO3. To put it all together: the starting amount of calcium needs to be 130 (needed for alkalinity precipitation) + 120 (desired left-over in water) = 250 ppm CaCO3. The water starts with calcium worth 110 ppm CaCO3 hence we need to add 140 ppm CaCO3. This equals a calcium addition of about 56 mg/l which you can get from about 240 mg/l gypsum or from ~200 mg/l calcium chloride.

Calculating the lime is a bit more difficult since you need to consider the chemical reactions that are happening and you also need to condider the residual amount of free CO2 and carbonic acid in the water. For this you need the water pH. Assuming a pH of 8 I see that you need about 100 mg/l lime.

I can test my water with my pH meter. However, for simplicities sake, what would happen if I jacked my calicum ppms up to about 250 with gypsum and added a 1/4 cup of slaked lime per 5 gallons and followed the procedure outlined on your site? Is this going to knock my alkalinity down suffficiently? I realize it may cause a ph change in the water, as well.

Sorry, I hate to have to have it dumbed down that much for me but I am just curious how simple you can make this.

Adding more calcium then what is needed is not a problem but blindly adding slaked lime doesn't work. If you add more than what is needed to precipitate alkalinity you will increase the alkalinity of the water again. But not by increasing (bi)carbonate but by increasing the hydoxide content of the water. These are the hydroxide ions that were added in excess of the available bicarbonate and carbonic acid and which didn't find anything to react with. They will give the water a high pH and, just like bicarbonate, fight the acidity of the grist and can lead to a high mash pH.

what would happen if I jacked my calicum ppms up to about 250 with gypsum and added a 1/4 cup of slaked lime per 5 gallons.

Yikes that's a lot of lime. I figured out my rate by trial and error. I've been adding about 1-1.5 tsp for 10 gal of water (carbonates ~250 ppm). I recall reading somewhere that the reaction to from chalk is VERY quick and therefore one can judge how much to add by watching the pH. Once you have added enough lime to precipitate the carbonates, the pH will start to go up rapidly due to the excess of hydroxide ion as Kai said